Ut cachinnis dissolvatur torqueatur rictibus
Всем полопаться от смеха, скорчиться от хохота
Kahkahalarla gülünsün, gülmekten katılınsın
May we all collapse in laughter, giggling uncontrollably
The first one is a medieval Latin phrase from "Coena Cypriani" quoted by Umberto Eco in Il Nome Della Rosa.
Video ridere certe quem scurra Crescentius,
Ut cachinnis dissolvatur, torqueatur rictibus;
Sed prius pedens crepabit tussiendo vetulus,
Quam regat linguam contemptus prior balbus omnibus.
http://books.google.com/books?id=WPlLl1PNegQC The second one is a great Russian translation by Elena Kostyukovich.
The third one is a Turkish translation that is great phonetically. It may have followed the original rhythm, but Turkish stressing is very difficult to my ears, so I do not know for sure. See the "Olympus" (uludağ) dictionary
http://www.uludagsozluk.com/The fourth one is an attempt to gain in rhythm while losing in style from "Let him be convulsed with laughter, let him be twisted into a gaping grin!"
I could find a lot of translations that I think do not keep the rhythm, such as:
„Да се скъса от прекален смях, да криви в смях устата си!“ (Bulgarian)
"che si dissolva con le risate, che gli angoli della bocca si torcano" (Italian)
I think the verse rhythm is more important than its meaning, style, vocabulary or even rhyme.
Are there any other rhythmical translations?